Tungsten Ore Decomposition Process – Sodium Hydroxide

Sodium hydroxide is the main agent for tungsten ore decomposition process. Tungsten concentrate has high purity, can be easily decomposed, so use NaOH is easy and environmental friendly. So NaOH plays an important role in tungsten ore decomposition process.

Sodium hydroxide is also called caustic soda, it has strong corrosion property, it is in flake or block shape, can be easily soluble in water to form alkali solution.

Chemical formula of NaOH decomposing tungsten concentrate :
FeWO₄+2NaOH=Na₂WO₄+FeOH₂  or
MnWO₄+2NaOH=Na₂WO₄+MnOH₂

Unfortunately, after years of exploration, tungsten concentrate is facing problem of scarcity. Tungsten scheelite then becomes main resource. In the early times, scientists try to use NaOH to dissolve scheelite, the result is unsatisfactory. Especially concentrate and scheelite mixed tungsten deposition, NaOH becomes useless.

However, scientists do not give up the research. Finally they proved that NaOH can be used to decompose scheelite. By hot ball mill process, NaOH can be used to decompose tungsten scheelite and concentrate shceelite mixed mineral. It has high efficiency and decomposing rate and becoming one of the main methods to decompose scheelite.

Chemical formula of NaOH decomposing tungsten scheelite:
CaWO₄(s)+2NaOH(aq)=Na₂WO₄(aq)+Ca(OH)₂(s)

It is proved that when pH value ＜5.9, Ca2+ concentration increases, tungsten scheelite can not exist stably. When pH value ＞13.6, tungsten scheelite can be decomposed into Ca(OH)2 and Na2WO4. In a word, as long as NaOH has high concentration, tungsten scheelite can be decomposed thoroughly.

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